In general, a conventional puncture-durable tire has a structure as shown in FIG. 1. It is structured to have a tire body 10 embedded with filament reinforcing elements 20, on the inside top of which is covered with a PVC layer 30 in a secondary treatment in a production process. The PVC layer 30 is added in mixture with a DOP oily chemical in the secondary treatment so as to make the tire not apt to leak when it is punctured by a pointed object.
Such a prior art tire has the following disadvantages:
1. The rubber side walls of such a tire is relatively weak to protect the tire from deformation on the side walls when the tire is not filled with enough air, resulting in driving jeopardy.
2. The PVC layer 30 produced in the secondary treatment during production will easily become hardened and chapped or peeled off the tire because of a centrifugal force resulted from the spinning of a tire. Thus, the gravity center of the tire is shifted in operation, causing danger in driving.
3. The surface of the PVC layer 30 becomes oily and sticky as a result of addition of the DOP chemicals, and it prevents a punctured tire from being patched with ease.